The present invention relates to powder-actuated tools and, more particularly, to means for adjusting the power level of indirect-acting power actuated fastener driving tools.
Powder-actuated fastener driving tools, of the indirect-acting type, comprise, in general, a piston, the rear end of which slides into an expansion chamber for the gases produced by the combustion of the propelling charge.
It is known in the art to continuously adjust the power level of such tools by modifying the initial volume of the expansion chamber through relative axial displacement of two chamber-defining tool parts. Such a displacement may for example, be realized by screwing one part, including the cartridge chamber, onto another part which includes stop means defining the piston battery position.
It is also known in the art to provide a safety interlock, for such tools, preventing tool discharge unless the tool muzzle is firmly pressed against the work piece. Such an interlock may, for example, be realized by a barrel slideably carried in the tool receiver and biased toward a forward or loading position, and a firing mechanism operable only when the barrel is in a rearward or battery position. Further, the receiver, which is telescoped over the barrel, may be adapted to limit access thereto, such that rearward displacement of the barrel may be accomplished only when the tool is substantially perpendicular to the work surface. This feature is commonly known as angle-fire control and is intended to prevent discharge of the tool under conditions wherein ricochet of the fastener may occur.
Unfortunately, the above-described power adjustment technique alters the axial relation of the barrel and the receiver. It is, therefore, presently impossible to incorporate in such a tool, both the power adjustment and constant angle-fire control features.